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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1171

Livsmedelsföretags problematik i omställningen till återvinningsbar plastanvändning / Food companies’ problems in the transition to recyclable plastic use

Tveiten, Kristoffer January 2020 (has links)
This study aims to identify problems that food companies may encounter during the transition from un-recyclable plastic packaging, to recyclable plastic packaging. The study is based on a survey and a case study. The survey was answered by 16 food companies who, with their signature of the Plastinitiativet 2022, have taken responsibility for increasing the recyclability of their plastic packaging. The case study focuses on a food company that may want to sign Plastinitiativet 2022, but first need to know more about their current plastic usage and what possibilities they have to increase the recyclability of their plastic package. Both studies show that food companies may experience some problems in the transition to a more recyclable plastic usage. A change in the plastics material and color may result in unexpected problems. Multilaminates and barrier materials have special functions but lower the recyclability. Laser marking and/or minimal printing, labels, shrink labels and adhesives on the packaging do not appear to be problematic for most of the companies. Signing Plastinitiativet 2022 seems to motivate the food companies to take measures, to increase the recyclability of their plastic packaging. All food companies will probably encounter problems of varying severity. The severity varies depending on the type of plastic used at present and the type of food that is packaged. The transition is also likely to contribute to higher materials- and staff costs for food companies.
1172

Processing and Reliability Assessment of Solder Joint Interconnection for Power Chips

Liu, Xingsheng 18 April 2001 (has links)
Circuit assembly and packaging technologies for power electronics have not kept pace with those for digital electronics. Inside those packaged power devices as well as the state-of-the-art power modules, interconnection of power chips is accomplished with wirebonds. Wirebonds in power devices and modules are prone to resistance, noise, parasitic oscillations, fatigue and eventual failure. Furthermore, there has been an increase demand for higher power density and better efficiency for power converters. Power semiconductor suppliers have been concentrating on improving device structure, density, and process technology to lower the on-resistance of MOSFETs and voltage drop of IGBTs. Recent advances made in power semiconductor technology are pushing packaging technology to the limits for performance of these power systems since the resistance and parasitics contribution by the package and the wirebonds are roughly the same as that on the silicon. In recent years, an integrated systems approach to standardizing power electronics components and packaging techniques in the form of power electronics building blocks has emerged as a new concept in the area of power electronics. As a result, it has been envisioned that the packaging of three-dimensional high-density multichip modules (MCMs) can meet the requirement for future power electronics systems. However, the conventional wirebond interconnected power devices are excluded from three-dimensional MCMs because of their large size, limited thermal management, and incompatible processing techniques. On the other hand, advanced solder joint area-array technologies, such as flip-chip technology, has emerged in microelectronics industry due to increased speed, higher packaging density, and performance, improved reliability and low cost these technologies offer. With all these benefits to offer, solder joint area-array technology has yet to be implemented for power electronics packaging. Therefore, the first objective of this study is to design and develop a solder joint area-array interconnection technique for power chips. Solder joint reliability is a major concern for area array technologies and power chip interconnection, thus the second objective of this study is to evaluate solder joint reliability, investigate the fatigue failure behavior of solder joint and improve solder joint reliability by developing a new solder bumping process for improved solder joint geometry, underfilling solder joint with encapsulant and applying flexible substrate in the assembly. The third objective is the implementation of solder joint interconnection technique in developing chip-scale power packages and a three-dimensional integrated power electronics module structure. Solder joint area array interconnection for power chips has been designed with the considerations of parasitic resistance and inductance reduction, current handling capability, thermal management, reliability improvement and manufacturability. A new solder joint fabrication process, which is able to produce high standoff hourglass-shaped solder joint that consists of an inner cap, middle ball and outer cap, as well as the conventional solder bumping process have been successfully developed for power chips by using stencil printing. This solder bumping technology is compatible with the existing surface-mount assembly operations and potentially low cost. The fabricated solder joints have been characterized for their structure integrity, mechanical strength and electrical performances. Solder joint reliability has been improved by optimizing solder joint geometry, underfilling flipped power chip and utilizing compliant substrate. Solder joint reliability was evaluated using accelerated temperate cycling and adhesion tests. The interfaces of the triple-stacked solder joints were examined using scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) for the integrity of the joint. Acoustic microscopy imaging (nondestructive evaluation) was utilized to examine the quality of the bonded interfaces and to detect cracks and other defects before and during accelerated fatigue tests. Adhesion strength of both single bump barrel-shaped and stacked hourglass-shaped solder joints to bonding pads was characterized and analyzed. It was found that stacked hourglass-shaped solder joint have higher fracture stress than barrel-shaped solder joint. This verifies that hourglass-shaped solder joint has lower stress singularity at the interface between the solder bump and the silicon die as well as at the interface between the solder bump and substrate than barrel-shaped solder joint, especially around the corners of the interfaces. Furthermore, the adhesion strength of barrel-shaped solder joint decreases much faster than that of high standoff hourglass-shaped solder joint under temperature cycling, which indicates that the latter has high reliability than the former. Our accelerated temperature cycling test clearly shows that solder joint fatigue failure process consists of three phases: crack initiation, crack propagation and catastrophic failure. Solder joint geometry, underfilling and substrate flexibility were proved to affect solder joint reliability. The effects of solder joint shape and standoff height on reliability have been systematically studied experimentally for the first time. Our experimental results indicated that both hourglass shape and great standoff height could improve solder joint fatigue lifetime, with standoff height being the more effective factor. The fatigue lifetime of high standoff hourglass-shaped solder joint is improved mainly by prolonged crack propagation time, with slight improvement in crack initiation time. Experimental data suggested that shape is the dominant factor affecting crack initiation time while standoff height is the major factor influencing crack propagation time. Underfilling and flexible substrate improved the lifetime of both barrel and hourglass-shaped solder joints. The effect of underfill on solder joint reliability is well known in microelectronics packaging field. However, for the first time, it is reported in this study that flex substrate could improve solder joint reliability. It has been found that flex substrate bucks during temperature cycling and thus reduces thermal strain in solder joints, which in turn improves solder joint fatigue lifetime. Chip scale packaging can enable a few very important concepts and advantages in power electronics packaging. It offers high silicon to package footprint ratio, provides a known good die solution to power chips, improves electrical as well as thermal performance and creates an opportunity for power component standardization. Two kinds of chip-scale power packages have been developed in this research. One is called cavity down flip chip on flex; the other is termed Die Dimensional Ball Grid Array (D2BGA). Both utilize solder joint as chip-level interconnection. Electrical tests show that the VCE(sat) of the high speed IGBT chip-scale packages is improved by 20% to 30% by eliminating the device¡¯s wirebonds and other external interconnections, such as leadframe. Double-sided cooling is realized in these CSPs. Temperature cycling test shows that the CSPs are reliable. Integrated power electronics modules (IPEMs) are envisioned as integrated power modules consisting of power semiconductor devices, power integrated circuits, sensors, and protection circuits for a wide range of power electronics applications, such as inverters for motor drives and converters for power processing equipment. We have developed a three-dimensional approach, termed flip chip on flex (FCOF), for packaging high-performance IPEMs. The new concept is based on the use of solder joint (D2BGA chip scale package), not bonding wires, to interconnect power devices. This packaging approach has the potential to produce modules having superior electrical and thermal performance and improved reliability. We have demonstrated the feasibility of this approach by constructing half-bridge converters (consisting of two IGBTs, two power diodes, and a simple gate driver circuitry) which have been successfully tested at power levels over 30 kW. Switching tests have shown that parasitic inductance of the FCOF module has been reduced by 40% to 50% over conventional wire bond power modules. Better thermal management can be achieved in this three-dimensional power module structure. Compared with the state-of-the-art half-bridge power modules, the volume of the half-bridge FCOF power module is reduced by at least 65%. Reliability test shows that this flip chip on flex power module structure is potentially more reliable than wire bond power module. / Ph. D.
1173

Use of Antimycotics, Modified Atmospheres, and Packaging to Affect Mold Spoilage in Dairy Products

Grove, Tina Moler 04 April 2000 (has links)
The effects of natamycin, oxygen scavengers and a 25% CO₂:75% N₂ modified atmosphere on the growth of <I>Penicillium roqueforti</I> in shredded cheddar and mozzarella cheese stored at 10°C for 0, 60, 120, or 180 day was studied. Microbiological and sensory testing was assessed on 0, 7, 14 and 21 days after opening. Carbon dioxide decreased (P<0.05) as O₂ (P>0.05) and N₂ (P>0.05) increased throughout storage. Cheddar and mozzarella cheeses were stored for 180 and 60 days, respectively without significant (P> 0.05) increases in yeast and mold populations. Fungal populations increased significantly (P< 0.05) after packages were opened. Differences in yeast and mold (YM) counts during storage and once the packages were opened were independent of natamycin application and presence, O₂ scavengers and inoculated <I>Penicillium roqueforti</I> for both types of cheeses. Growth of <I>Penicillium roqueforti, Aspergillus niger, Geotrichum candidum</I> and <I>Neosartorya fischeri</I> were evaluated in atmospheres of 0:30:70, 0.5:29.5:70, 1:29:70, 2:28:70, and 5:25:70, O₂:CO₂:N₂ over a 5-day period. Spores were cultured on antibiotic-supplemented potato dextrose agar (pH 5.6, a<sub>w</sub> 0.95) and incubated at 25°C. All four molds germinated and grew at 0.5:29.5:70. Extent of mycelia growth diameter (mm) increased significantly (P<0.05) as oxygen concentration increased from 0.5% to 5%. All growth was inhibited at 0:30:70, but germination and growth occurred once cultures were exposed to 20.9% atmospheric O₂, indicating that a modified atmosphere containing no residual O₂ is fungistatic. Yeast and mold growth was seen in ultra-pasteurized (UP) extended shelf-life fluid milk stored at (7.2°C). Ten half-pint, pint, quart and half gallon filled cartons were randomly selected from all UP products available. Samples, pulled at random on day 0, 15, 30, 45, and 60, were plated on Yeast and Mold Petrifilm™. Forty-seven percent of the UP products stored for 45 days tested positive for mold. Fungal growth was apparent down the side and along the bottom of the 5th panel. Contamination was traced to the presence of yeast and mold spores in paperboard cartons. Pinholes were present in the polyethylene coating and wicking occurred at the unskived 5th panel. Fungi of similar origin and fatty acid profile were isolated from UP milk products and the paperboard cartons. / Ph. D.
1174

Effect of modified atmosphere packaging on growth of Listeria monocytogenes and nonproteolytic Clostridium botulinum in cooked turkey

Lawlor, Kathleen A. 03 March 1999 (has links)
The growth of Listeria monocytogenes and nonproteolytic Clostridium botulinum type B spores in cooked, uncured turkey was investigated separately under varying conditions of modified atmosphere packaging (MAP), refrigerated and temperature-abuse storage, and lactic acid bacteria (LAB) competition. L. monocytogenes (LM) growth was suppressed when initially outnumbered 3.5 logs:1 or 2.1 logs:1 by naturally-occurring LAB, but not when the initial LAB:LM population ratio was equivalent. Lowering storage temperature from 10 degrees to 4 degrees C enhanced the inhibitory effect of CO₂ in the packaging atmosphere, and extended the period of product olfactory acceptability. When the LAB:LM population ratio was equivalent, objectionable odors were not detected in most of the samples, despite LAB counts in excess of 10E⁸/g. This raises concerns with respect to public health, since high levels of L. monocytogenes can be present in MAP meat and poultry products without accompanying signs of overt spoilage. Cellular fatty acid (CFA) analysis was a valuable tool for distinguishing between phenotypically distinct isolates of LM inoculated into MAP turkey. Fatty acid composition of foodborne outbreak-associated (serotype 4) and non-outbreak-associated (serotype 1) strains of LM correlated with antigenic type (4 or 1) and agglutination reaction (granular or flocculent). Strain ATCC 43256 (serotype 4b) produced a consistently unique CFA profile, making it the easiest of the four test strains to be differentiated. Analysis of additional LM serotypes, as well as examination of existing clinical and environmental CFA databases for correlations between fatty acid profiles and diagnostic characteristics of LM, is necessary before CFA analysis can be effectively applied as an epidemiological tool for tracking the distribution of LM strains in food products and throughout the farm-to-table food chain. Reduced storage temperature significantly delayed botulinal toxin production and extended the period of olfactory acceptability of cooked turkey, but even strict refrigeration did not prevent growth and toxigenesis by nonproteolytic C. botulinum type B. Toxin was detected on day 7 for product stored at 15 degrees C and on day 14 for product stored at 10 degrees C, irrespective of packaging atmosphere. At 4 degrees C, toxin was detected on day 14 for product packaged without carbon dioxide, and on day 28 for product packaged with 30% carbon dioxide. At all three storage temperatures, toxin detection preceded or coincided with olfactory unacceptability, demonstrating the potential for consumption of toxic product when spoilage-signalling sensory cues are absent. / Ph. D.
1175

Actividades logísticas y su relación en la importación de productos farmacéuticos de la subpartida nacional 3004.90.24.00 durante el periodo 2014 - 2018 en el sector privado / Logistics activities and their relation with imports of pharmaceutical products of national subheading 3004.90.24.00 during the years 2014 to 2018 in the private sector

Chan Perochena, Rocío Valery, Montalvo Estrada, Martha Guissel 30 July 2020 (has links)
En el Perú las importaciones de medicamentos oncológicos y VIH han venido creciendo en durante los años, a pesar de su alto valor. Este escenario se debe a la falta de inversión en I+D para la industria local, así como al incremento de pacientes de estas enfermedades. Es por ello, que la presente investigación tiene como fin analizar las principales actividades logísticas y su relación con las importaciones de productos farmacéuticos de la subpartida nacional 3004.90.24.00 durante los años 2014 al 2018 en el sector privado. En primer lugar, se realizó una descripción de las variables en base a sus antecedentes y bases teóricas. En segundo lugar, para poder validar las hipótesis de la investigación se utilizó un enfoque cuantitativo, en base a un diseño no experimental, transversal y correlacional, para lo cual se elaboró una encuesta dirigida a los importadores representativos de medicamentos oncológicos y VIH. Finalmente, bajo resultados estadísticos se determinó que existe una relación positiva moderada fuerte entre las actividades logísticas con las importaciones de la subpartida nacional estudiada; asimismo, se pudo obtener resultados para cada subvariable de las actividades logísticas, es decir, transporte, almacenaje y embalaje, los cuales indicaron tener relación con las importaciones tratadas en la investigación. / Imports of oncological drugs and HIV in Peru have been growing over the years, despite their high value. This scenario is due to the lack of investment in R&D for the local industry, as well as the increase in patients with these diseases. That is why the purpose of this research is to analyze the main logistics activities and their relation with imports of pharmaceutical products of national subheading 3004.90.24.00 during the years 2014 to 2018 in the private sector. First, a description of the variables was made based on their antecedents and theoretical bases. Secondly, in order to validate the research hypotheses, a quantitative approach was used, based on a non-experimental, cross-sectional and correlational design, for which a survey was conducted for representative importers of oncological drugs and HIV. Finally, under statistical results it was determined that there is a strong moderate positive relation between logistics activities with imports of the national subheading studied. Additionally, it was possible to obtain results for each subvariable of the logistical activities, that is, transportation, storage and packaging, which indicated that they were related to the imports treated in the investigation. / Tesis
1176

Use of Gamma Radiation, Chemicals, and Packaging Films to Control Post Harvest Diseases and to Extend Refrigerated Life of Strawberries and Cherries

Cooper, Gerald M. 01 May 1961 (has links)
In recent years there has been a considerable amount of work done on developing chemicals that would inhibit mold growth when applied to fresh fruit, and at the same time, be acceptable to man when taken orally. This would save many thousands of tons of fresh produce that are lost each year by spoilage before it ever reaches the consumer. Along with the development of new chemicals to inhibit mold growth there is a substantial amount of research being done on developing a packaging film that will prevent recontamination of the produce, at the same time allowing the passage of gasses into and out of the package to allow respiration of the fruit. During the present century much emphasis has been placed on growing certain varieties of fruit for our specific needs. It has been found that particular varieties are better for canning and that other varieties are better for freezing. With the release of atomic energy for peaceful use in 1933 by the United States Congress, a new era of food preservation was introduced. Men in the scientific fields believe it is possible to extend the shelf-life of fresh fruits without altering their physical condition to great extent. Many institutions have been awarded grants and contracts to work on various phases of food preservation with atomic energy. Utah State University was awarded a contract by the United States Army Quartermaster Corp to study the use of gamma radiation for extending the shelf-life of fresh produce. It was with this idea in mind that work for this thesis was conducted to study the effects of gamma radiation, fungicides, and packaging film on the microbial growth on certain varieties of strawberries and cherries. In addition, experiments were conducted using fungicides and packaging films in order to lower the dose of radiation necessary to prevent mold growth. In order for this method of preserving fresh fruit to become successful, new and more economical methods and techniques in handling the materials will have to be developed.
1177

Optimisation des propriétés barrière de matériaux polymères par association avec des composés inorganiques pour des applications biomédicales : influence des approches nanocomposites et dépôts de couches minces siliciées / Combination of polymer materials with inorganic composents for biomedical packaging with improved barrier properties : influence of nanocomposite approach and silicon based thin layers deposition

Charifou, Romina 10 December 2013 (has links)
De par leur faible coût, leurs propriétés mécaniques ajustables et leur potentielle transparence, les matériaux polymères sont des candidats de choix pour le packaging biomédical. Cependant, il est souvent nécessaire d'améliorer leurs propriétés barrière à O2 et H2O afin de garantir une conservation optimale du produit conditionné. Dans ce contexte, l'approche choisie a été d'associer une phase inorganique à la matrice polymère. Ainsi, après un choix des systèmes polymères les plus adaptés aux conditionnements pharmaceutiques souples d'une part et rigides d'autre part, nous avons étudié deux voies d'optimisation des propriétés barrière : le dépôt de couches minces organosiliciées à la surface du polymère et la voie nanocomposites. Le but est d'établir pour ces deux types de systèmes hétérogènes les relations Structure/Morphologie/Propriétés. Le dépôt de couches minces organosiliciées a été effectué par le procédé de dépôt chimique en phase vapeur assisté par plasma. Nous avons étudié deux types de monocouches, la première de type céramique SiOx et l'autre de type SiCH. La combinaison de ces couches sous forme d'empilements sur le substrat polymère permet, outre l'augmentation conséquente des propriétés barrière, une meilleure conservation des propriétés fonctionnelles sous des sollicitations de type thermique ou mécanique. Les nanocomposites ont été préparés par voie fondu à partir d'un poly(propylène) et de charges oxyde de zinc ou doubles hydroxydes lamellaires. Nous avons étudié les effets d'un agent compatibilisant et de modifications de surface des charges. Les propriétés barrière sont reliées à l'état de dispersion des charges et aux interactions charges/matrice / Due to their good handling properties, potential transparency and low cost, polymers are key components for the biomedical industry. However, high barrier properties towards gases or vapors are required for packaging applications in order to retain the quality of the product. To achieve the improvements in barrier properties of polymers, two different ways based on the combination of an inorganic phase with the polymer material were studied. The aim was to establish Structure/Morphology/Properties relationships. Thin inorganic coatings deposited on polymer substrates are of particular interest for improving barrier properties. In the current work, thin transparent silicon based layers were deposited on flexible polymer films by plasma-enhanced chemical vapor deposition. Monolayers (SiOx type and SiCH type) and piles with an alternation of these different monolayers were studied. The interest of multilayer barrier coatings was highlighted for higher barrier properties and resistance to solicitations such as thermal treatment or mechanical deformation. The second approach consisted in preparing poly(propylene) based nanocomposites with inorganic nanoparticles such as zinc oxide and layered double hydroxides. The transport properties of these materials depend on the quality of the filler dispersion in the polymer, but also on the interface between the fillers and the polymer matrix. Thus, the influence of a compatibilizer and of the nanoparticle surface modification was investigated on the properties of the nanocomposites
1178

Developing a Four-Point Bending Apparatus to Measure Bending Stiffness of Corrugated Board

Singh, Manjeet January 2021 (has links)
No description available.
1179

Investigating Shareholder Social Activism From an Issue-Selling Perspective—Issues, Strategies, and Success

Zhao, Xiaoping 08 October 2013 (has links)
Building on the logic of issue selling, my dissertation explores the micro-processes of shareholder social activism through which shareholders interact with targeted firms and also addresses which micro-processes could affect the effectiveness and the success of shareholder social activism. To do this, my dissertation develops a theory with respect to the approaches of linguistically framing the contents of and of presenting shareholder social activism. Based on a qualitative (descriptive) analysis on 1,612 shareholder social proposals, my dissertation identifies six packaging strategies that are used by the proponents to linguistically frame the contents of their proposals and two selling strategies used by the proponents to present their proposals. Subsequently, a quantitative analysis demonstrates that the effectiveness of shareholder social proposals would be largely determined by the joint effects of opportunity framing, threat framing, coalition building, and repeated submitting and that other packaging strategies would have little unique contribution to the effectiveness and the success of shareholder social activism. I argue that my dissertation would make contributions to the understanding of shareholder social activism and also offer some theoretical considerations for future studies on issue selling, although my dissertation might not directly contribute to the body of work of issue selling. / Ph. D.
1180

Branding vlastní značky s přesahem do obalového designu / The Branding of an Original Logo Including Packaging Design

Domorád, Petr January 2016 (has links)
This thesis deals with the development of my own brand, primarily by defining the basic and important information on the topic. Introduces the development of their own brand, its name, logo, color, character and visual forms. A key element of the silkscreen printed prototypes paper products and their presentation on the Web.

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